The International Standard for anti-Rh (anti-D) Incomplete Blood-Typing Serum

Some time ago the WHO Expert Committee on Biological Standardization asked the National Institute for Medical Research, London, to consult with the WHO International Blood Group Reference Laboratory concerning the establishment of an international standard for albumin-potentiated anti-Rh(o) (anti-D) blood-typing serum. This paper describes the collection and testing of sera, the removal of unwanted antibodies, the pooling of the sera and the distribution in equal amounts in 3350 ampoules, which were subsequently freeze-dried. The titres were determined by 29 laboratories in 21 countries by means of four methods-suspension in albumin, replacement with albumin, enzyme (papain) treatment and the anti-human-globulin test. On the basis of the results obtained, the material has been established as the International Standard for Anti-Rh(o) (Anti-D) Incomplete Blood-Typing Serum and the International Unit has been defined, with the agreement of the participants in the collaborative study, as the activity contained in 0.95 mg of the International Standard for Anti-Rh(o) (Anti-D) Incomplete Blood-Typing Serum.